防止横竖屏时，iphone自动缩放的一段代码

function orientation_change() {
var viewport = document.querySelector('meta[name="viewport"]');
if (window.orientation == 0 || window.orientation == 180)
viewport.setAttribute("content", "width=device-width, maximum-scale=1.0, initial-scale=1.0, user-scalable=no");
else if (window.orientation == -90 || window.orientation == 90)
viewport.setAttribute("content", "width=device-height, maximum-scale=1.0, initial-scale=1.0, user-scalable=no");
}

window.onorientationchange = orientation_change;